A study of the reduced states of four isomeric bidiazines (diaza-2,2'-bipyridines) by UV-VIS/NIR-spectroelectrochemistry

Singly and doubly reduced forms of the four isomeric bidiazines 2,2'-bipyrazine, 3,3'-bipyridazine, 2,2'- and 4,4'-bipyrimidine have been generated in a spectroelectrochem. cell and studied by UV-visible/near-IR spectroscopy. As derivs. of 2,2'-bipyridine the compds. exhibit several groups of vibrationally structured long-wavelength bands in the paramagnetic anion radical state. The assignments and variations of transition energies depending on the diaza perturbation may be rationalized using CNDO/S CI calcns. on SciFinder(R)